Explain the significance of the discovery of Archaeopteryx: Why did this fossil demonstrate beyond reasonable doubt that birds share an ancestor with some reptilian groups?

It has characteristic more reptilian than birdlike. Although it had feathers and could fly, it had similarities to dinosaurs, including its teeth, skull, lack of a horny bill, and certain bone structures. It also had a long bony tail, claws in its wings, and a flexible s shaped neck. In 1868, Thomas Henry Huxley interpreted the Archaeopteryx fossil to be a transitional bird having many reptilian features. Using the fossils of Archaeopteryx and Compsognathus, a bird-sized and bird-like dinosaur, Huxley argued that birds and reptiles were descended from common ancestors. In 1986, J. A. Gauthier looked at over 100 characteristics of birds and dinosaurs and showed that birds belonged to the clade of coelurosaurian dinosaurs.